Selection Of Shelter For Crayfish(Procambarus Clarkii) And The Effect Of Shelter On Crayfish

Procambarus clarkii is a kind of cave animal for which caves are an important place to hide from predators and to avoid adverse environments.In the captive breeding of crayfish,some artificial materials are usually used as a substitute for caves,which are called shelters.However,there is no exact report on what kind of material,size or character of the shelter is used.Whether the shelter is necessary or the balance of advantages and disadvantages of shelter in breeding is also to be explored.In this paper,we set up experiments from two aspects:the selection of shelter by crayfish and the effect of shelter on crayfish,trying to explore the most suitable shelter environment for crayfish.Selection of shelter of crayfish:In the first experiment,selection of crayfish between two different shelters with one openings and two openings was set,then the selection ratio of the two shelters was calculated.The results showed that the female crayfish had no preference for two kinds of shelters,while the male crayfish had significant preference for one opening shelter on the first day of the experiment and at night.In the second experiment,selections of crayfish between shelters with diameters of 3.2 cm,4 cm and 5 cm,as well as with diameters of 5 cm,6.3 cm and 7.5 cm were set.Then the selection ratio of every shelter was calculated.The results showed that crayfish preferred medium size shelter with diameter about 1.5 times of body width.Female crayfish disliked shelters with oversize diameter or undersize diameter,and the males disliked shelters with undersize diameter but did not reject shelters with larger size.In the third experiment,selection of crayfish between shelters with lengths of single,double and treble body length,then the selection ratio of these shelters was calculated.The results showed that female crayfish preferred shelters that was twice or three times as long as crayfish body length,while males preferred shelter that was only of twice body length.In the fourth experiment,we set up three groups of selections between self-occupied shelter and blank shelter,shelter occupied by isosexual subjects and blank shelter,shelter occupied by heterosexual subjects and blank shelter.Crayfish can choose any one of the two shelters in each group,then the selection ratio of each shelter was calculated.The results show that the crayfish prefer to live in shelters occupied by themselves.Female crayfish preferred shelter occupied by isosexual subjects at the beginning of the experiment,and then the preference gradually decreases,while males had no preference for shelter occupied by isosexual subjects.Both male and female crayfish preferred shelter occupied by heterosexual subjects.The effect of shelter on crayfish:In the fifth experiment,juvenile and sub-adult crayfish were raised in a circular plastic box at a stocking rate of 1 individual per box,where a PVC pipe was placed in one group,and without PVC pipes as control group under the same conditions.The body length,body mass growth,survival rate and sheltering rate were measured.The results after two-month raising showed that shelters promoted the growth of the crayfish in the early growth stage,but with crayfish became bigger,the shelter's promotion weakened and eventually inhibited the growth.In the sixth experiment,crayfish of the same size were raised in a circular plastic box at a stocking rate of 1 individual per box,where a PVC pipe was placed in one group,and without PVC pipes as control group under the same conditions.The results showed that shelter had no effect on the motion activity of the crayfish.